Marantz 2245 User manual

"SERVICE.

_MANUAL

|

model

2245

|

Bgi

TABLE

OF

CONTENTS

CG

SECTION

7

:

PAGE

Introduction........

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Bo

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Galaens

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ays

2

Phono

and

Tone

pan

HStS

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imate

haa

Ysee

Baw

Sulstes

eaieice

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ane

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tees

ee

ais

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gest

4

Power

Amplifier

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cc's

6

dete

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SS

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SW

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CR

CES

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RR

Re

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SG

5

Power

Protection

Circuit

..

6...

0

cee

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2a

5

Speaker

Protector

Relay

Circuit

..

0.2.0.6.

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tee

mee

5

Suggestions

for

Trouble

Shooting

of

Power

Amplifier

Jahre

wie

hee

Beet

ae

Wage

le

De

GR

eds

6

Voltage

Conversion...

.....0

0c

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eseeenee

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6

Test

Equipment

Required

for

Servicing

...........-

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3,

23

ns

B

AM

Alignment

Procedure

.......

0.60

c

eee

ee

cece

eee

ence

nseeenstesessscens

er

ate

(A

FM

Alignment

Procedure

.......-..

ccc

cece

c

cece

erence

ttre

et

ee

tet

teene

me

.

&9

STEREO

Separation

Alignment

........

06.

ce

cece

eee

ee

tee

eee

-..

9

Muting

Circuit

Alignment..............-22-06%

signed

fe

Anh

a

bit

Gate

Gio

we

ere

eeate

ae

@

eta

10

Audio

Adjustment:

sc65

eshte)

ae

ih

etek

ee

eee

ROR

ee

eee

sa se

ee

aye

ssa,

oe

10

Parts:

List.

03

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ete

seas

a8

Bae

gt

geaaee

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Cena

tats

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BGR

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21

Specifications

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0.02

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-..29

LIST

OF

ILLUSTRATIONS

FIGURE

:

.

PAGE

1.

Remove

the

Terminal

Cover

........0

20:

e

eee

cece

eee

e

een

nee

mae

6

2.

Voltage

Conversion

Chart

..........

Tae

eRe

ea

lee

Rea:

Smee

oie,

tents

_7

3.

Lissajou

Figure

on

Oscilloscope

....

1.2...

ce

eee

nets

Tide.

tees

od

4,

Dial

Stringing.

.....

6.

ecw

ce

cere

c

cece

eet

eee

eet

ee

tere

eeee

-..11

5.

Front

Panel

Adjustment

and

Component

Locations

...........00c

cece

eeee

ere

WZ

6.

Main

Chassis

Component

Locations

(Top

View)

...........0050ee

eee

deat

tas

o%

~..12

7.

Rear

Panel

Adjustment

and

Component

Locations

................eeeeeees

-

«+.

13

8.

Main

Chassis

Component

Locations

(Bottom

View)

.............00e

eee

Sas

SS

9.

FM

Front

End

Assembly

P100

Component

Locations........

da

ic

deat

Sra

abner

Ba

-..

14

10.

FM

IF

Amplifier

Assembly

P200

Component

Locations

......

Nisbet

aneehats

4,6

a

tas

11.

FM

Detector

Assembly

P500

Component

Locations

.............22200

ee

eee

oe

15

12.

MPX

Stereo

Decoding

Amplifier

Assembly

P300

Component

Locations........

Scala

e.

BS

13.

Muting

Control

Amplifier

Assembly

P550

Component

Locations

.............

-

-..

16

14.

AM

Tuner

Unit

Assembly

P150

Component

Locations

.............0000

0

eee

e

wee

16

15.

Phono

Amplifier

Assembly

P700

Component

Locations

.............06+.e20

2 2

ee

17

16.

Tone

Amplifier

Assembly

P400

Component

Locations

.................0055

e

225.17

17.

Power

Amplifier

Assembly

P750

Component

Locations

..........

Sa

aaieth

tna

Jada

-

-«..

18

18.

Regulated

Power

Supply

and

Protection

Relay

Circuit

Assembly

P800

Component

Locations

..........

0.

cece

eee

ee

eee

tee

mae

19

19.

Loudness,

High

and

Low

Filter

and

Muting

Switch

Unit

Assembly

P6OO

Component

Locations

........

2...

ccc

eee

cette

eee

we

19

20:

Schematic

Diagranit

io.

sao

ook

Ps

ek

Sas

Ce

ede

eee

he

ies

Geer

i

20

5.

Power

Amplifier

The

signal

from

the

tone

amnplitiek

is

applied

to

the

differential

amplifier

(base

of

H751)

through

the

coupling

capacitor

C751.

The

differential

amplifier

provides

very

high

input

impedance

and

its

collector

output

(H752)

is

applied

to

the

base

of

H753

which

in

turn

applies

its

Output

to

the

H756

through

the

network

R766,

C762

and

R771,

and

to

the

H757

through

the

network

R776,

C763

and

R772.

The

outputs

of

H756

and

H757

are

applied

to

the

H758

and

H757

respectively.

HOO1

and

HOO2

are

power

transistors

used

in

complementary

symmetry

configulation

and

mounted

on

the

heat

sink.

To

maintain

overall

amplifier

stability

and

linearity,

degenerative

feed

back

is

utilized

throughout

the

amplifier.

This

feed

back

is

also

necessary

to

reduce

distortion

to

within

specified

limit.

The

RC

network

R775

and

C756

condition

the

feed

back

signal

for

the

audio

signals.

R759

and

C755

are

also

a

feed

back

loop

provided

to

obtain

a

stable

zero

DC

off

set

voltage

at

the

speaker

output

terminals.

The

R762

is

a

trimming

resistor

to

adjust

the

DC

off

set

voltage.

Dynamic

bias

is

applied

to

the

base

of

driver

transistors

H758

and

H757.

This

dynamic

bias

circuit

is

comprised

of

H761,

H760

and

R763.

This

provides

a

variable

base

bias

for

driver

transistors

that

automatically

maintains

the

proper

base

voltage

with

temperature

change.

The

temperature

sensitive

biasing

components

of

the

dynamic

circuit

are

thermally

couppled

through

a

heatsink

to

the

power

amplifier

transistors.

6.

Power

Protection

Circuit

Protection

circuit

for

the

amplifier

is

provided

by

sensing

resistor

networks

and

two

switching

transistors.

When

the

output

transistors

are

over-driven,

the

current

increase

through

the

power

output

transistor

causes

an

increased

current

flow

through

R789

(or

R788)

and

the

potential

across

the

R789

wil!

be

increased.

This

increased

voltage

potential

is

applied

to

the

base

of

H755

through

the

resistor

R783

and

turns

on

the

H755.

Since

the

collector

of

H755

is

directly

connected

to

the

base

of

H757,

this

means

that

the

base

of

H757

is

bypassed

to

the

ground

through

emitter-collector

path

of

H755.

Thus

the

input

signal

to

the

H757

is

restricted

to'the

value

which

maintains

the

operation

of

power

transistor

with

in

the

safety

area.

A

resistor

network

R777

and

R781

also

works

as

a

sensing

network.

When

the

center

voltage

(collector

voltage

of

power

transistors)

is

excessively

increased

to

a

positive

value

by

certain

troubles,

the

voltage

applied

to

the

base

of

H755

makes

the

H755

turn

on,

making

bypass

circuit,

and

protects

the

power

transistor.

For

the

other

half

cycle

of

driving

signal,

the

pperaung

principle

is

applied

provided.

7.

Speaker

Protector

Relay

Circuit

The

speaker

protection

cureant

consisting

of

H808,

H809,

H810,

etc

protects

the

speaker

systems

against

any

loud

“pop”

sound

developed.

This

circuit

is

so

designed

that

no

sound

is

heard

for

the

first

three

or

five

seconds

after

the

power

switch

is

turned

on

by

the

time

constant

circuit

consisting

of

C807

and

R816.

This

circuit

also

protects

the

speaker

systems

against

some

troubles

due

to

DC

off

balance

between

the

speaker

system

terminals

by

instantly

operating

the

relay

and

cut

off

the

speaker

systems

from

the

circuit.

When

DC

off

balance

valtage

(positive)

is

developed

between

speaker

terminals

by

possible

defects

such

as

broken.

power

transistor,

short-circuits,

or

broken

potentio

meter

R762,

as

the

base

of

H808

is

connected

to

the

speaker

terminal,

the

transistor

H808

is

turned

on

by

this

offset

voltage

developed

and

this

makes

the

transistor

H809

and

H810

turns

off,

thus

cutting

off

the

relay

and

disconnecting

the

speaker

from

the

output

circuit.

When

negative

offset

voltage

is

developed,

this

voltage

directly

turns

off

the

H809

and

H810,

thus

speaker

is

cut

off

from

the

circuit

and

protected.

The

circuit

also

protects

the

speaker

systems

from

the

possible

damage

when

the

amplifier

is

over-driven

by

very

tow

frequencies

such

as

7

or

lower

cycles.

|

8.

Suggestions

for

Trouble

Shooting

of

Power

Amplifier

8.1

Excessive

Line

Consumption

a.

Check

for

shorted

rectifiers

HOO5;

also

check

C007

and

COO8.

b.

Check.

for

shorted

transistors

H758

and

H759,

HOO1

and

HO02,

or

check

H760.

Check

for

open

control

R763,

and

bias

diode

H761.

Check

L004

for

short.

CAUTION:

BECAUSE

THE

DRIVER

AND

OUTPUT

STAGES

ARE

DIRECT

COUPLED

COMPONENTS

MAY

FAIL

AS

A

DIRECT

RESULT

OF

AN

INITIAL

COM-

PONENT

FAILURE.

IF

A

SHORTED

TRANSISTOR

OR

ZENER

DIODE

IS

FOUND,

OR

CONTROL

OR

BIAS

DIODE,

BE

SURE

TO

CHECK

THE

REMAINING

DRIVER

AND

OUTPUT

COMPONENTS

FOR

SHORT

OR

OPEN

CIRCUIT

BEFORE

RE-ENERGIZING

THE

AMPLIFIER.

8.2

No

Line

Consuniption

or

Zero

Bias

a.

Check

line

cord,

fuse,

transistors

H760,

HOO1,

HOO2.

HOO3

and

H004,

bias

diode

H761.

b,

Check

for

open

rectifier

HOO5,

or

open

L004.

8.3

No

DC

Balance

a.

Check

R762

and

Zener

diodes

H762

and

H763.

9.

Voltage

Conversion

This

model

is

equipped

with

a

universal

power

transformer

to

permit

operation

at

100,

120,

200,

220

and

240V

AC

50

to

60Hz.

To

convert

the

Model

2245

to

the

required

voltage

perform

the

following

steps:

(1)

Remove

the

top

cover.

(2)

Remove

the

Transformer

Wire

Connection

Terminal

Cover,

loosen

two

Cover

mounting

screws

on

the

rear

panel,

see

Fig.

1.

(3)

Change

the

jumper

wires

as

illustrated

in

Fig.

2

for

the

required

AC

voltage

and

replace

the

'

fuse

as

instructed.

CAUTION:

DISCONNECT

POWER

SUPPLY

CORD

FROM

AC

OUTLET

BEFORE

CONVERT-

ING

VOLTAGE.

REMOVE

SCREW

REMOVE

THIS

COVER

Figure

1.

Remove

the

Terminal

Cover

For

100

V

Operation

For

200V

pea

(Use

4A

Fuse

)

(Use

3A

Fuse

BROWN

GREEN

WHITE

RED

BLUE

YELLOW

BROWN

GREEN

WHITE

RED

BLUE

YELLOW

—

For

120

V

Operation

For

220V

Operation

(Use

3A

Fuse

)

(Use

3A

Fuse

)

BROWN

GREEN

WHITE

RED

BLUE

YELLOW

BROWN

GREEN

WHITE

RED

BLUE

YELLOW

For

240V

Operation

(Use

3A

Fuse

)

BROWN

GREEN

WHITE

RED

BLUE

YELLOW

Figure

2.

Voltage

Conversion

Chart

10.

Test

Equipment

Required

for

Servicing

Table

1

lists

the

test

equipment

required

for

servicing

the

Model

2245

Receiver.

Manufacturer

and

Model

No.

AM

Signal

Generator

Test

Loop

FM

Signal

Generator

Stereo

Modulator

Audio

Oscillator

Oscilloscope

VTVM

Circuit

Tester

AC

Wattmeter

AC

Ammeter

Line

Voltmeter

Variable

Autotransformer

(0-140VAC,

10

amps.)

Shorting

Plug

Output

Load

(8

ohms,

0.5%,

100W)

Output

Load

(4

ohms,

0.5%,

100W)

Less

than

0.3%

distortion

Less

than

0.3%

distortion

Weston

Model!

CVO-100P,

less

than

0.02%

residual

distortion

is

required.

High

sensitivity

with

DC

hori-

zontal

and

vertical

amplifiers.

With

AC,

DC,

RF

range

Simpson,

Model

390

Commercial

Grade

(1-10A)

Commercial

Grade

(0-15VAC)

Powerstat,

Model

116B

Use

phono

plug

with

600

ohm

across

center

and

shell.

Commercial

Grade

Commmercial

Grade

Signal

source

for

AM

align-

ment

Used

with

AM

Signal

generator

Signal

source

for

FM

_align-

ment

Stereo

separation

alignment

and

Trouble

Shooting

Sinewave

and

squarewave

sig-

nal

source.

Waveform

analysis

and

trouble

shooting,

and

ASO

alignment.

Voltage

measurements

Trouble

Shooting

Monitors

primary

power

to

Amplifier.

Monitors

amplifier

output

un-

der

short

circuit

condition.

Monitors

potential

of

primary

power

to

amplifier.

Adjusts

level

of

primary

power

to

amplifier.

Shorts

amplifier

input

to

elimi-

nate

noise

pickup.

Provides

8-ohm

load

for

ampli-

fier

output

termination.

Provides

4-ohm

load

for

ampli-

fier

output

termination.

protection

relay

has

been

operated

or

not.

(When

the

relay

has

been

operated,

no

signal

is

provided

to

the

speaker

terminals.)

If

there

is

no

signal

at

the

speaker

terminals,

turn

off

the

system

power

of

the

amplifier

for

about

one

minutes,

then

again

turn

on

the

power

and

adjust

the

R782

and

R783

for

a

slight

increased

height

of

A

and

B.

6.7

For

the

another

Main

Amplifier,

repeat

the

procedures

6.2

to

6.6.

co)

10

20

30

40

50

60-70

80

Vce(V)

Figure

3.

Lissajou

Figure

on

Oscilloscope

8

XQ

NN

START

FINISH

SS

_

1

Nee

POINTER

Figure

4,

Dial

Stringing

11

12

Tuning

Knob

S60I-4

S0O05-I1

SO05-2

S003

JOO9

MOO!

MOI7

S004-2S6O0I-|

S60I-2

sS60I-3

=

teedble

halar\ce

volurn|

JOO8

SO04-I

-

SO02

R469

R470

R47I

ROOS

ROOG6

JOIO

Figure

5.

Front

Panel

Adjustment

and

Component

Locations

P800

PI0O

P500

PI50

P500

HAL

ee

er

BRR

EE

Ns

mePert

la:

HOO!

HOO2

TIGKIE

SY

ist

100]

£2

lta

a

Na

P750

C007

coos

Jolgs

LOO4

P550

L75i

P750

Figure

6.

Main

Chassis

Component

Locations

(Top

View)

JOO02

SPEAKE|?

SYSTEMS

JOO3

ZOOW

MEX

TOTAL}

1OOW

frax

TOTAL

JOIZ

Jol2

JOI!

P700

LOO!

soo!

JOO!

QUADRADIAI

°

3

oe

JO2O0

JOO6

JOO7

JOIS.

VyOOS

Figure

7,

Rear

Panel

Adjustment

and

Component

Locations

P450

P400

P2000

Cd

a

I

wil

a

cd

i’

aE

,

Ct

Figure

8.

Main

Chassis

Component

Locations

(Bottom

View)

|

HI

|

le

im)

Jons

FM

Front

End

Assembly

P100

Component

Locati

igure

9.

F

ier

Assembly

P200

Component

Locations

Figure

10.

FM

IF

Ampli

14

Marantz 2245 User manual

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